1973 Dodge Dart Sport won’t run right or stay running

What ignition ECU? I had an Orange box that would would overheat while driving and would just kill the motor. Roll a few feet and you could start the car again and drive on. Those ECO cases need grounded too, a lot of people miss that.

I've read where the tank not venting can cause a similar problem. When it dies, pull over and pop the cap. If it difficult to remove or makes a vacuum suck sound then you know its not venting.